And so to bending the sides. You will recall I made a luthier’s bending iron from a piece of water pipe and a heat gun, well here it is in action bending the sides, or bouts of the mandolin.

The first bend was the upper bout for the top quadrant to the right of the neck – this would be the least conspicuous if I made a mistake.

I ensured the bending iron was at the right heat – so water misted onto it boiled immediately

luthier's bending iron

I had the bouts soaking in a tub of water for about 20 minutes. They had been thinned to just under 2mm with the wasp sander mounted on my drill stand. They probably needed to be a little thinner still – more like 1.0-1.5mm thick for easier bending.

Once the iron was hot enough I donned leather welding gloves – so my fingers wouldn’t get burnt if I made a mistake – and picked up the bout and the metal bending sheet that I had made earlier. The bending sheet provides support to the fibres of the timber and helps to hold the steam in the wood. I’ll explain in a moment how I made the backing strap.

luthier's bending iron
I gently worked the timber, springing it slightly and pressing with a wrapping motion against the bending iron. You can feel it reach the right temperature and the point at which it wants to bend. Don’t rush this because – as I found – if you try to go too hard too quickly you will snap the timber and have to start over. It’s best to have a test piece or two so you can practice first on a non-critical component. Here is another view of the process.

luthier's bending iron

Within about two hours I had all the bouts shaped and clamped to the body so they would dry and retain their shape. Blackwood is notorious for springing back to its original (flat) shape. I left it overnight to cool.

The bending iron worked well. I would get it really hot on the 600C setting then when it reaches operating temperature I dialed it back to 300C to maintain heat without stressing the heat gun too much.

Making the bending strap
The strap is quite simple to make. you need an empty steel food tin (washed carefully) with the top and base removed. I cut it open with tin snips/shears. Next I took two small size tent pegs and bent them in a vise into a triangle – these will form the handles so you are not dealing with a sharp tin amidst the heat! I folded the ends of the tin can around the tent peg on the side where the two ends meet, and hammered it so it made a good round shape around the tent peg, leaving about a centimetre (say half an inch) and drilled three holes and joined it with three pop-rivets. Complete the other end and voila – you have a luthier special tool bending iron backing strap!

luthier bending strap

Tomorrow is glue-up time!

Cheers
Jerry

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